Richard Ting's K99/R00 application We have recently published the application of new 18F-PET/NIRF (Positron emission tomography/Near Infrared Fluorescence) multimodality imaging probes on the polydextran ligand Lymphoseek (tilmanocept, Neoprobe), a ligand currently in phase III clinical trials as a 99mTc labeled species for detecting lymphatic breast cancer metastasis. The K99 phase of this research applies this recent success to very different new molecules including peptides and proteins. We will apply the PET/NIRF probe to Angiopep 2, a 3 kD peptide for imaging drug transport across the blood brain barrier, and to 55 kD anti-CEA T84.66 diabody, a genetically engineered class of antibodies for imaging CEA positive tumors. These applications will allow us develop superior tracers for imaging colorectal cancer and drug transport. Another goal of the proposed K99 research is the generation of a library of different Integrin ?v?3 antagonists conjugated to PET/NIRF probes of differing molecular weights and charge. The imaging of this library will allow us to simultaneously select for the best probes for imaging tumor angiogenesis by PET and allow us to generate both PET and NIRF databases on the behavior of different moieties in vivo. This database would allow us to rationally design new drugs that accumulate in specific tissues (PET) while retaining the sub-cellular localization and inhibitory properties (observed by NIRF) for which they were selected. Data from the imaging of this library can be used to deliberately alter the in vivo biodistribution of new pharmaceuticals or select for probes that are specific for different forms of cancers. The first R00 phase aim attempts to advance PET/NIRF technology by exploiting the fact that fluorescence is the modality of choice for high-throughput drug screening, We will modify the cancer probes developed in the K99 with immobilizing technology to generate arrays that can indicate small changes in tumor biology, such as increased tumor aggressiveness, and help determine a patient's treatment regime. Desired compounds can be released from the array using aqueous 18F, to generate a PET probe, or combination of probes for corroborative in vivo imaging. The fluorophore on the array will then be substituted with photodynamic therapy (PDT) agents allowing for the selection of probes for PET guided endoscopic PDT applications. Finally, a new application that allows for kit-like radiotracer labeling will be applied to a new library of PET/NIRF small molecules that are capable of demonstrating intracellular transport. These molecules will possess exterior functionality that is similar to clinical 99mTc tracers in order to address the problem of recurrin 99mTc shortages, a current problem in nuclear medicine today.